Benign Hyperphenylalaninemia


Type of disease: Rare conditions

Benign hyperphenylalannemia (H-PHE) is a rare genetic condition resulting from a mutation (error) in a person’s DNA. People with H-PHE are unable to breakdown the amino acid phenylalanine. It is an amino acid disorder. The protein we get from food is broken down into its amino acids (its building blocks). We typically eat more protein than needed; therefore we often have more amino acids than we need. Enzymes (special proteins) breakdown the extra amino acids into harmless products our body can get rid of. If one of the enzymes needed is missing or not working correctly, the amino acid may not be broken down. The buildup of the amino acid can damage our body. In this case there is not enough of the enzyme, phenylalanine hydroxylase (PAH). A baby with H-PHE thus can break down phenylalanine but not as quickly as a baby whose has enough PAH.

Changes in the PAH gene cause H-PHE and it is an autosomal recessive condition. H-PHE is a less severe form of classic phenylketonuria (PKU) because less phenylalanine builds up. Due to this, babies with H-PHE usually do not show any signs or symptoms. If a baby were to show signs, the symptoms may include mild intellectual difficulties and developmental delays, irritated skin, or vomiting. H-PHE may be treated with a special diet which limits the amount of phenylalanine that goes into the body. Early diagnosis and treatment have been shown to be effective in improving the health of individuals affected by this condition. Many babies are screened at birth so that treatment may begin early, however the conditions included in newborn screening vary state by state. For more information, visit Baby’s First Test. Talk with your doctor about the most current treatments. Support groups also are a good source of information. A genetic counselor will help you understand the genetics.

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